At IU, where can I find help documentation for Imail or Umail?

Important:

UITS is preparing to retire the Imail service, and no new Imail accounts are being created. If you are currently using Imail, you are not affected at this time. You will have at least six months' notice before Imail is discontinued. For more, see About the Imail retirement.

Imail

Microsoft offers a FAQ page for Outlook Web App, which contains help for web-based access to Imail.